The development of a two stroke engine is a significant challenge even though they have been around for years. The thermal efficiency of a two stroke engine has historically been better than its four stroke competitor. The historic two stroke engines have been operated in more steady power output applications and more for a power to weight advantage. The transient control of a two stroke engine while getting the absolute best fuel economy will be a challenge for modern two stroke engines applied to on highway vehicles.
The inventor has recognized that control of the blower device (i.e., supercharger or other air boosting apparatus) is critical because power is required to operate these devices, and that the general goal should be to consume as little power for these devices as possible to get the best fuel economy possible. This leas to be done over varying altitude and ambient conditions. In the past, blower devices have typically operated based on a fixed ratio to the engine speed. Blower device size would typically be selected for a worst-case scenario and fuel would have to be adjusted as conditions changed. At high altitudes, for example, engine power level would be significantly reduced and/or temperature rises in the cylinder line, the piston, and the exhaust system would occur.
In accordance with another aspect of the invention, a method for controlling an air boosting apparatus in a two-stroke, opposed piston engine, is provided, the air boosting apparatus being arranged to boost air pressure in a charge air stream upstream of a cylinder of the engine. The method comprises operating the air boosting apparatus as a function of a first engine speed, a first torque demand, and one or more first ambient conditions to provide a first pressure ratio (PR) of pre-turbine pressure (PTP) versus turbocharger compressor discharge pressure (CDP) and a first air-to-fuel ratio (AFR), registering a change in at least one first ambient condition of the one or more first ambient conditions to a second ambient condition, and adjusting operation of the air boosting apparatus in response to the registered change from the first to the second ambient condition to provide a second PR and a second AFR.
In accordance with another aspect of the invention, a method for controlling an air boosting apparatus in a two-stroke, opposed piston engine, is provided, the air boosting apparatus being arranged to boost air pressure in a charge air stream upstream of a cylinder of the engine. The method comprises operating the air boosting apparatus as a function of a first engine speed, a first torque demand, and a first altitude to provide a first pressure ratio (PR) of pre-turbine pressure (PTP) versus turbocharger compressor discharge pressure (CDP) and a first air-to-fuel ratio (AFR), registering a change in altitude to a second altitude, and adjusting operation of the air boosting apparatus in response to the registered change from the first to the second altitude to provide a second PR and a second AFR.
In accordance with another aspect of the invention, a method for controlling an air boosting apparatus in a two-stroke, opposed piston engine, is provided, the air boosting apparatus being arranged to boost air pressure in a charge air stream upstream of a cylinder of the engine. The method comprises operating the air boosting apparatus as a function of a first engine speed and a first torque demand to provide a first pressure ratio (PR) of pre-turbine pressure (PTP) versus turbocharger compressor discharge pressure (CDP) and a first air-to-fuel ratio (AFR), registering a change in the first torque demand to a second torque demand, and adjusting operation of the air boosting apparatus in response to the registered change from the first to the second torque demand to provide a second PR and a second AFR.
In accordance with another aspect of the invention, a method for controlling an air boosting apparatus in a two-stroke, opposed piston engine, is provided, the air boosting apparatus being arranged to boost air pressure in a charge air stream upstream of a cylinder of the engine. The method comprises operating the air boosting apparatus as a function of a first engine speed, a first torque demand, and first transient rate to provide a first pressure ratio (PR) of pre-turbine pressure (PTP) versus turbocharger compressor discharge pressure (CDP) and a first air-to-fuel ratio (AFR), registering a change from the first transient rate to a second transient rate, adjusting operation of the air boosting apparatus in response to the registered change from the first to the second transient rate to provide a second PR and a second AFR.
In accordance with another aspect of the invention, a method for controlling an air boosting apparatus in a two-stroke, opposed piston engine, is provided, the air boosting apparatus being arranged to boost air pressure in a charge air stream upstream of a cylinder of the engine. The method comprises operating the air boosting apparatus as a function of at least one of
a first engine speed,
a first torque demand,
a first altitude,
a first transient rate, and
one or more first ambient conditions
to provide a first pressure ratio (PR) of pre-turbine pressure (PTP) versus turbocharger compressor discharge pressure (CDR) and a first air-to-fuel ratio (AFR), registering a change in the at least one of
the first engine speed to a second engine speed,
the first torque demand to a second torque demand,
the first altitude to a second altitude,
the first transient rate to a second transient rate, and
the one or more first ambient conditions to one or more second ambient conditions, and adjusting operation of the an boosting apparatus in response to the registered change to provide a second PR and a second AFR.
In accordance with another aspect of the present invention, a two-stroke, opposed piston engine comprises an air boosting apparatus arranged to boost air pressure in a charge air stream upstream of a cylinder of the engine; and a controller arranged to operate the air boosting apparatus as a function of at least one of
a first engine speed,
a first torque demand,
a first altitude,
a first transient rate, and
one or more first ambient conditions
to provide a first pressure ratio (PR) of pre-turbine pressure (PTP) versus turbocharger compressor discharge pressure (CDP) and a first air-to-fuel ratio (AFR), register a change in the at least one of
the first engine speed to a second engine speed,
the first torque demand to a second torque demand,
the first altitude to a second altitude,
the first transient rate to a second transient rate, and
the one or more first ambient conditions to one or more second ambient conditions, and adjust operation of the air boosting apparatus in response to the registered change to provide a second PR and a second AFR.